adv7196a Analog Devices, Inc., adv7196a Datasheet - Page 21

• Manufacturer Part Number: adv7196a
• Description: Encoder With Three 11-bit Dacs, 10-bit Data Input, And Macrovision
• Manufacturer: Analog Devices, Inc.

FILTER GAIN
FG (FG7–FG0)
(Address (SR4–SR0) = 10H)
Figure 34 shows the various operations under the control of the
Filter Gain register
FG BIT DESCRIPTION
Filter Gain A (FG3–FG0)
These bits are used to program the gain A value, which varies
from response –8 to response +7 and are applied to Filter A.
Filter Gain B (FG4–FG7)
These bits are used to program the gain B value, which varies
from response –8 to response +7 and are applied to Filter B.
Refer to Sharpness Filter Control and Adaptive Filter Control
section for more detail.
GAMMA CORRECTION REGISTERS 0–13
(GAMMA CORRECTION 0–13)
(Address (SR5–SR0) = 14H–21H)
The Gamma Correction Registers are fourteen 8-bit-wide register.
They are used to program the gamma correction Curves A and B.
Generally, gamma correction is applied to compensate for the
nonlinear relationship between signal input and brightness level
output (as perceived on the CRT). It can also be applied wherever
nonlinear processing is used.
Gamma correction uses the function:
where γ = gamma power factor.
Gamma correction is performed on the luma data only.
The user has the choice to use two different curves, Curve A or
Curve B. At any one time only one of these curves can be used.
FG7
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
FILTER GAIN B
FG6
FG7–FG4
.
FG5
Signal
0
1
2
3
4
5
6
7
–8
–7
–6
–5
–4
–3
–2
–1
OUT
FG4
= (Signal
FG3
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
IN
FILTER GAIN A
FG2
) γ
FG3–FG0
FG1
0
1
2
3
4
5
6
7
–8
–7
–6
–5
–4
–3
–2
–1
FG0
The response of the curve is programmed at seven predefined
locations. In changing the values at these locations the gamma
curve can be modified. Between these points linear interpolation
is used to generate intermediate values. Considering the curve to
have a total length of 256 points, the seven locations are at: 32,
64, 96, 128, 160, 192, 224.
Location 0, 16, 240, and 255 are fixed and can not be changed.
For the length of 16 to 240 the gamma correction curve has to be
calculated as below:
where:
y = gamma corrected output.
x = linear input signal.
γ = gamma power factor.
To program the gamma correction registers, the seven values for
y have to be calculated using the following formula:
where:
x
n
y
Example:
y
y
y
y
The above will result in a gamma curve shown below, assuming a
ramp signal as an input.
n
32
64
96
128
Rounded to the nearest integer.
(n–16)
= [(16/22
= [(48/22
= [(80/22
= [(112/22
= Value for x along x-axis at points:
= 32, 64, 96, 128, 160, 192, or 224.
= Value for y along the y-axis, which has to be written into
300
250
200
150
100
50
0
y
the gamma correction register.
0
n
= [
GAMMA CORRECTION BLOCK OUTPUT
TO A RAMP INPUT
4)0
4)0
4)0
x(n–16)
4)0
5
5
5
.5
50
/(240 – 16)]
2 24] + 16 = 76
224] + 16 =120
224] + 16 = 150
224] + 16 = 147
SIGNAL INPUT
100
y = x
0.5
LOCATION
SIGNAL OUTPUT
γ
γ
150
(240) – 16) + 16
ADV7196A
200
250